THIS invention relates to a preload headboard for an elongate prop.
In underground mine stoping practice, elongate props, typically having timber as their major component, are used widely to provide yielding support for the hanging wall of the stope. Conventionally, elongate props are cut to length to suit the stope width and are then installed normal to the reef plane. A wedge or headboard is hammered between the upper end of the prop and the hanging wall. This serves to wedge the prop in position but applies very little axial preload force to the prop.
A more substantial preload force is desirable since a prop which is already compressively stressed is in a better state to accept the substantial loads imposed by the hanging wall.
It has already been proposed to preload an elongate prop by placing a bag on a headboard on top of the prop, inflating the bag with a settable grout so that the bag presses on the hanging wall and applies an axial compressive force to the prop, and allowing the grout to set to maintain the applied force.
It is an object of this invention to provide a headboard suitable for supporting the bag.